Petroleum asphalt is originated from crude oil processing and refining. The increasingly diminution in resources inevitably leads to scarcer petroleum asphalt. Due to the present excessive exploitation and overuse, petroleum resources are in danger of exhaustion. According to the scientists' prediction, petroleum resources will be exhausted by the middle of the century, namely, around 2050.
The current situation of petroleum resources and the issue of environment development compel us to unremittingly search for and apply novel and renewable alternative materials. At the present, biomass energy, which is researched and developed by the whole world sparing no effort, is a kind of inexhaustible and renewable energy. Thanks to its properties of having widely available raw materials, renewability and biodegradability, this kind of material has taken the pace of industrialization.
There are abundant biomass resources. Take China as an example, there are about 0.7 billion tons of agricultural and sideline products which can be used as energy, wherein the annual output of crop straw is about 0.6 billion tons and the annual output of other agricultural wastes is about 0.13 billion tons; the forest biomass resources which can be used for energy are about 0.3 billion tons each year; and the annual production of municipal solid waste is about 0.25 billion tons. Moreover, compared with fossil energy, biomass energy is environmentally friendly and renewable, which can be regarded as two outstanding advantages.
At present, pyrolysis is the main technical means of bio-energy production and utilization. Biomass pyrolysis, also known as thermal cracking or cracking, usually refers to a process in which biomass is heated in an environment without or lacking oxygen, causing molecular decomposition and thus generating coke, condensable volatile component and gas products, wherein the condensable volatile component is rapidly cooled to flowable liquid and bio-oil or tar in a yield of about 40% to 60% is thereby formed. The crude oil of bio-oil generated through pyrolysis should go through further processing such as classification, purification and separation to obtain gasoline, diesel, methanol, ethanol fuel oil and chemical products.
Usually, the currently produced bio-oil is directly burned as low-level fuel. However, the characteristics of the heavy component of bio-oil are very close to those of asphalt for road, and thus bio-oil can be modified as asphalt for road construction, that is, bio-asphalt, which can not only achieve recycling of relative “wastes” in energy and chemical industry field, turning waste into treasure, but also form a complementary production system of recycling economy.
Bio-asphalt obtained by subjecting bio-oil to extraction process and oxidation process has good adhesion and thus can be used for paving roads. In order to further improve crack resistance at low temperature, the method for improving asphalt performance through modification is commonly used. By adding petroleum asphalt and macromolecular materials to bio-asphalt, bio-asphalt will have considerably enhanced fatigue resistance and significantly reduced temperature sensitivity, and will show good crack resistance at low temperature.
This method for preparing bio-asphalt is characterized in simple process, easy operation and convenient implementation. In addition, bio-oil, the raw material for preparing bio-asphalt is not limited to that rich in lignin, and thus the raw materials for bio-asphalt preparation are more adaptable.